Forest Condition in Latvia1
Madis Sipols2
Abstract
Systematic assessment and observation (survey, inventory) of forests in Latvia has been underway since the
1700’s. Latvia’s forests are in the boreal/temperate forest zone and cover 44 percent of the country. Forest
growing conditions are subdivided into five site class types: forests on dry mineral, wet mineral, wet peat,
drained mineral, drained peat soils. The dominant tree species in Latvia are Scots pine (Pinus sylvestris
L.), 39.7 percent; Norway spruce (Picea abies Karst.), 20.6 percent; and common birch (Betula pendula
Roth.), 28.4 percent. Systematic assessment of air pollution impacts on forest health in Latvia was started in
1990 by the International Cooperative Program on Assessment and Monitoring of Air Pollution Effects on
Forests - ICP Forests. Assessment methods were changed to the USDA Forest Service’s Forest Health Monitoring Program in 1994. Assessments of forest ecosystems in Latvia show the alteration and disappearance
of stand structure of typical, common forest ecosystems (especially Scots pine stands) , and the invasion of
plant species non-typical to these forests, which has been caused by human activities and air pollution
(sinantropization). It has also been found that Norway spruce stands will be endangered in the near future
because of their sensitivity to environmental factors, and that currently forest stand health is mainly affected
by localized entomological damage (insect and fungal diseases). In addition, environmental pollution has
caused biological destabilization in forest ecosystems.
Introduction
Latvia is one of three small Baltic countries transitioning to a free market economy.
Latvia occupies 64,000 km2, and 44 percent is covered by forests, which are of great
importance for the stability of the economy, landscape, environment, and flora and
fauna of Latvia. The first forest inventory in Latvia was carried out in 1788 for the
Lencu estate. Inventories of all the biggest estate forests were done until the beginning of the 1900’s. Then the process was periodically repeated after intervals of 10
to 15 years, including measurement and assessment of a forest stand and its health
condition. On this basis long-term forest changes, even for 100 years, were assessed.
During the late 1900’s, when environmental pollution significantly increased,
there was a necessity for more comprehensive forest assessment methods. In 1990
the European program, “International Cooperative Program on Assessment and
Monitoring of Air Pollution Effects on Forests (ICP Forests),” was implemented all
over the territory of Latvia. In 1994 establishment of sample plots for the Forest
Health Monitoring (FHM) program was started. This program is a component of
the United States’ Environmental Monitoring and Assessment Program (EMAP).
This paper discusses the current status of forests in Latvia as determined by
the newly implemented Forest Health Monitoring Program.
1 An abbreviated version of this paper
Forest Composition
The forests in Latvia are in the boreal/temperate forest zone. The total area covered
by forests has changed substantially over time. Agriculture lands freed from forests have been reforested as a result of various events such as wars or plague. The
productive forest area has changed from 25 percent in 1923 to 27 percent in 1949, 38
percent in 1973, and 44 percent 1995 (fig. 1).
USDA Forest Service Gen.Tech.Rep. PSW-GTR-166. 1998.
was presented at the International
Symposium on Air Pollution and Climate Change Effects on Forest Ecosystems, February 5-9, 1996, Riverside,
California.
2 Chief Engineer, Latvian Institute of
Forest Inventory, Riga Street 113,
Salaspils, Latvia LV-2169.
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Session IV
Forest Condition in Latvia
Sipols
Figure 1 — Forest cover in
Latvia by percent.
-<30
-30-40
-41-50
-51<
-forestry
Forest growing conditions in Latvia are varied and include dry mineral soils
(58 percent), wet mineral (10.4 percent), wet peat (12.0 percent), drained mineral
(9.6 percent), and drained peat (10 percent). The main tree species in Latvia are
Scots pine (Pinus sylvestris) (39.7 percent), Norway spruce (Picea abies) (20.6 percent), common birch (28.4 percent), common alder (2.4 percent), aspen (2.5 percent), and grey alder (5.5 percent) (fig. 2). All forests are divided into three categories according to their functions and importance (ecological, economical, etc.):
●
●
●
Protected forests
(9.6 percent)
Nature reserves
38,700 ha
National park forests
51,600 ha
Nature park forests
15,000 ha
Nature protected forests
87,600 ha
Soil protected forests
72,200 ha
Restricted management forests (16.3 percent)
Landscape forests
55,100 ha
Green zone forests
244,000 ha
Environment protection forests 225,700 ha
Commercial forests
(74.1 percent).
Scots pine occupies the greatest part of the forests in all three categories. Scots
pine is also widely represented through all soil types — from sandy to fertile soils,
as well as in peat soils. Scots pine is a biologically stable tree species, stable in
windstorms, and relatively less damaged by insects and fungi diseases. Compared
with Norway spruce, Scots pine is more resistant against various stresses and often
reaches 150 to 300 years. However, for the last 20 years the condition of pine
stands have been deteriorating. When the European system of forest monitoring was carried out from 1990 to 1995, Scots pine had a high level of defoliation for all age classes — 30.0 percent in 1990, 33.2 percent in 1992, and 24.1
percent in 1995 (table 1).
Forest Damage
The methodology of the FHM system is different from the previous systems and
uses more detailed condition indicators. About 40 percent of the planned sample
plots are established. The first results of this research show that the crown density
282
USDA Forest Service Gen.Tech.Rep. PSW-GTR-166. 1998.
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Forest Condition in Latvia
Sipols
Figure 2 — Distribution of Scots
pine (Pinus sylvestris L.) in Latvia.
LIMBAZI'
VENTSPILS
VALMIERA
VALKA
ALUKSNE
TALSI
CBSIS
OULBENE
KULDIGA
BALVI
RIGA
TUKUMS
MADONA
OGRE
SALDUS
TELGAVA
DOBELE
LIEPÁJA
AIZKRAUKLE
BAUSKA
REZEKNE
IBKABPILS
LEGEND
Average percentage share of pine stands
20
25 30 35 40
45
50 55 60
LUDZA
PREILI
KRASLAVA
DAUGAVPILS
65
Table 11— Changes in defoliation by most represented tree species (1990-1995).
Tree species
Scots pine
Norway spruce
Common birch
Common alder
Aspen
1990
<60
27.0
12.9
16.3
10.6
13.2
>60
Percentages of defoliation by mean age classes (years)
1992
1993
1991
<60
>60
<60
>60
<60
>60
1994
<60
>60
1995
<60
>60
32.2
23.8
17.9
7.7
15.1
28.9
14.8
18.7
14.1
15.0
27.1
14.3
14.5
11.6
17.5
27.2
19.4
18.3
10.3
16.5
24.1
13.6
13.1
13.4
14.5
24.1
18.3
16.3
9.6
15.0
33.0
20.5
18.8
9.0
18.2
31.6
15.6
19.5
14.3
18.3
34.1
21.1
21.1
11.5
20.3
29.1
15.3
18.1
14.1
18.3
30.4
20.3
19.5
12.2
18.4
of conifers on average is less than the broadleaved species (figs. 3,4). Usually crown
damages are associated with different insects. For example, in 1995 high levels of
defoliation of Scots pine in the vicinity of Riga was associated with Gilpinia pallida
Kl. and Lymantria monacha L. The total damaged area there was about 10,000 ha. In
1992/93 Pissodes piniphilus Herbst caused serious crown damage on Scots pine.
At the same time invasion of new uncommon plant species in the forests on
dry sandy soils have been observed during the last 10 years. At several levels these
new species have become dominant. Scots pine stands undergo the process of
sinantropization, and the natural characteristics of these forests have changed and
disappeared.
The second most important tree species is Norway spruce, which is biologically unstable and very sensitive towards secondary factors such as insect damage
and fungus diseases. Currently, Norway spruce is seriously endangered. ICP Forests monitoring data from 1995 shows that 8 percent of all observed spruce are
damaged, and 70 percent are damaged by Ips typographus L.
Forest health is closely related to environmental changes (air pollution, climate,
urbanization, etc.). An important environmental quality indicator is the national
emission of SOx , NOx , CO, particulate pollution, and other substances. The total
emission amount of gases and particulate matter from 1991 to 1995 has decreased.
In 1991 the total emission of gases and solid substances was 144,100 tons/year; in
1992 — 92,310 tons/year; in 1993 — 87,130 tons/year; in 1994 — 103,840 tons/year;
and in 1995 — 86,440 tons/year (fig. 5).
USDA Forest Service Gen.Tech.Rep. PSW-GTR-166. 1998.
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Forest Condition in Latvia
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Figure 3 — Crown density of
Scots pine in Latvian forests (FHM
plots established in 1994, 1995).
LEGEND
DENSITY (pct)
26 - 35
36 - 45
46 - 55
56 - 65
66 - 75
pine isn't represented
(or is represented only with
intermediate, overtopped trees)
Figure 4 — Crown density of
Norway spruce in Latvian forests
(FHM plots established in 1994,
1995).
LEGEND
DENSITY (pct)
26 - 35
36 - 45
46 - 55
284
56 - 65
66 - 75
spruce isn't represented
(or is represented only with
intermediate, overtopped trees)
USDA Forest Service Gen.Tech.Rep. PSW-GTR-166. 1998.
Session IV
Forest Condition in Latvia
Sipols
Figure 5 — Total emissions of
gases, solids, and other substances
(tons/year) in Latvia in 1995.
> 1500
1600 - 2500
2600 - 3500
< 3500
districts
Summary
The area covered by forests in Latvia has increased in recent years. Health of trees
is mainly affected by local entomological damages including cyclical repetition of
insect damages. During recent years intensity of insect damage has not reached the
catastrophic levels observed in earlier years. Environmental pollution impact on
ecosystems has also changed forest stand structure (especially in Scots pine stands)
and a process of biological destabilization has been observed
Acknowledgments
I thank Laurie Dunn for technical editing of this manuscript.
USDA Forest Service Gen.Tech.Rep. PSW-GTR-166. 1998.
285